package com.ccx.coachsite.ui.customview;

import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.Scroller;

import com.ccx.coachsite.data.SystemConst;

/**
 * 支持横向滑屏ViewGroup <br>
 */
public class ViewPager extends ViewGroup {
	static final String TAG = "ViewPager";

	private static final int TOUCH_STATE_REST = 0;
	private static final int TOUCH_STATE_SCROLLING = 1;
	private static final int SNAP_VELOCITY = 600;

	private int mCurScreen;
	private int mTouchSlop;
	public int init = SystemConst.NO_DATA;
	private int mTouchState = TOUCH_STATE_REST;
	private boolean isFirstLayout = true;
	private float mLastMotionX, mLastMotionY;

	private IPageBar tab;
	private Scroller mScroller;
	private VelocityTracker mVelocityTracker;

	public ViewPager(Context context) {
		super(context);
		initWorkspace(context);
	}

	public ViewPager(Context context, AttributeSet attrs) {
		super(context, attrs);
		initWorkspace(context);
	}

	public ViewPager(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
		initWorkspace(context);
	}

	private void initWorkspace(Context ctx) {
		mScroller = new Scroller(ctx);
		mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);

		final int width = MeasureSpec.getSize(widthMeasureSpec);
		final int count = getChildCount();
		for (int i = 0; i < count; i++) {
			getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
		}
		if (isFirstLayout) {

			if (init != SystemConst.NO_DATA && init >= 0
					&& init < getChildCount())
				scrollTo(init * width, 0);
			else
				scrollTo((getChildCount() - 1) / 2 * width, 0);

			isFirstLayout = false;
		}
	}

	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		int childLeft = 0;

		final int count = getChildCount();
		for (int i = 0; i < count; i++) {
			final View child = getChildAt(i);
			if (child.getVisibility() != View.GONE) {
				final int childWidth = child.getMeasuredWidth();
				child.layout(childLeft, 0, childLeft + childWidth,
						child.getMeasuredHeight());
				childLeft += childWidth;
			}
		}
	}

	public void snapToDestination() {
		int screenWidth = getWidth();
		int destScreen = (getScrollX() + screenWidth / 2) / screenWidth;
		snapToScreen(destScreen);
	}

	public void snapToScreen(int whichScreen) {
		whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
		if (getScrollX() != (whichScreen * getWidth())) {
			final int delta = whichScreen * getWidth() - getScrollX();
			int duration = Math.abs(delta) * 2;
			if (duration > 500)
				duration = 500;

			mScroller.startScroll(getScrollX(), 0, delta, 0, duration);
			mCurScreen = whichScreen;
			invalidate();
		}
	}

	public void setToScreen(int whichScreen) {
		isFirstLayout = false;
		whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
		mCurScreen = whichScreen;
		scrollTo(whichScreen * getWidth(), 0);
	}

	@Override
	public void computeScroll() {
		// Log.d(TAG, "ViewPager.computeScroll");
		if (mScroller.computeScrollOffset()) {
			scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
			postInvalidate();
			if (tab != null) {
				tab.scrollHighLight(mScroller.getCurrX());
				if (mScroller.isFinished()) {
					int page = mScroller.getFinalX() / getWidth();
					tab.updateSelected(page);
				}
			}
		}
	}

	@Override
	public boolean onTouchEvent(MotionEvent event) {
		if (mVelocityTracker == null) {
			mVelocityTracker = VelocityTracker.obtain();
		}
		mVelocityTracker.addMovement(event);

		final int action = event.getAction();
		final float x = event.getX();
		final float y = event.getY();

		switch (action) {
		case MotionEvent.ACTION_DOWN:
			if (!mScroller.isFinished()) {
				mScroller.abortAnimation();
			}
			mLastMotionX = x;
			mLastMotionY = y;
			break;

		case MotionEvent.ACTION_MOVE:
			int deltaX = (int) (mLastMotionX - x);

			mLastMotionX = x;
			mLastMotionY = y;
			scrollBy(deltaX, 0);
			if (tab != null)
				tab.scrollHighLight(this.getScrollX());
			break;

		case MotionEvent.ACTION_UP:
			final VelocityTracker velocityTracker = mVelocityTracker;
			velocityTracker.computeCurrentVelocity(1000);

			int velocityX = (int) velocityTracker.getXVelocity();
			if (velocityX > SNAP_VELOCITY && mCurScreen > 0) {
				snapToScreen(mCurScreen - 1);
			} else if (velocityX < -SNAP_VELOCITY
					&& mCurScreen < getChildCount() - 1) {
				snapToScreen(mCurScreen + 1);
			} else {
				snapToDestination();
			}

			if (mVelocityTracker != null) {
				mVelocityTracker.recycle();
				mVelocityTracker = null;
			}
			mTouchState = TOUCH_STATE_REST;
			break;
		case MotionEvent.ACTION_CANCEL:
			mTouchState = TOUCH_STATE_REST;
			break;
		}

		return true;
	}

	@Override
	public boolean onInterceptTouchEvent(MotionEvent ev) {
		final int action = ev.getAction();
		if ((action == MotionEvent.ACTION_MOVE)
				&& (mTouchState != TOUCH_STATE_REST)) {
			return true;
		}

		final float x = ev.getX();
		final float y = ev.getY();

		switch (action) {
		case MotionEvent.ACTION_MOVE:
			final int xDiff = (int) Math.abs(mLastMotionX - x);
			final int yDiff = (int) Math.abs(mLastMotionY - y);
			if (xDiff > mTouchSlop && yDiff < mTouchSlop && xDiff > yDiff) {
				mTouchState = TOUCH_STATE_SCROLLING;
			}
			break;

		case MotionEvent.ACTION_DOWN:
			mLastMotionX = x;
			mLastMotionY = y;
			mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST
					: TOUCH_STATE_SCROLLING;
			break;

		case MotionEvent.ACTION_CANCEL:
		case MotionEvent.ACTION_UP:
			mTouchState = TOUCH_STATE_REST;
			break;
		}
		return mTouchState != TOUCH_STATE_REST;
	}

	public void setTab(IPageBar tab) {
		this.tab = tab;
	}

	public void setInitTab(int tab) {
		this.init = tab;
	}
}
